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Vetiver Grass: an Option for Erosion Control in Hilly Regions of Bangladesh- Prospects and Limitations

J. U. Shoaib
PSO
Retired as CSO , SRDI.

Abstract/ Executive Summary:

Due to geographical position hill areas of Bangladesh experience intensive downpour during the monsoon, June to August. Rainfall intensity frequently exceeds 100mm hr^-1 for 15 minutes duration. Total annual rainfall is around 2800mm (as recorded at SCWMC). Soils are shallow with erosivity factor ranges from 0.36 to 0.54. The terrain is exposed for raindrop splash during the early monsoon. Shifting cultivation, massive deforestation, fuel wood collection, infrastructure development and other land uses without appropriate conservation measures cause accelerated erosion. The general situation at present leads to severe land degradation in hilly region. It was estimated that soil loss from steep slope (where k=0.37) is about 42 t ha-1 yr^-1 under shifting cultivation and total loss yr^-1 from about 32,500 hectare is 1.5 million ton. The loss is reduced to 6-11 t ha-1 yr^-1 by using hedgerow along contour in shifting cultivation. It was observed that performance of vetiver as hedge crop is the best with respect to soil retention as well as management aspect.

Keywords: Hilly areas, Vetiver grass, Soil eroson, Hrdge

Location: SCWMC, Banderban

Start Date: 01-01-1996

End Date: 31-12-1998

Program Area: Risk Management in Agriculture

Commodity: Land erosion

Objectives:

Performance study of vetiver grass as hedgerow crop for erosion control in hilly regions of Bangladesh.

Methodology:

Choice of species: Choice of species for hedgerow has carried different degrees of weights by users and researchers. Generally local or indigenous species are favored and the choice depends on: # its perennial and coppicing habit, drought tolerance, pruning or trimming resistance (preferably leguminous). # its ability to grow in a wide range of soils, tolerance to submergence, resistance to diseases, pests and insects. # multipurpose use, easily manageable and easy to propagate. Retrospect and prospect of hedgerow use in Bangladesh: Bangladesh spreads over three different physiographic entities viz. Hills (12%), Terraces (8%), and Floodplains (80%). Soil erosion is spectacular all over the country. Very little work was done to quantify the extent. But as normal practices farmers are used to allow grasses like Cynodon ductylon to grow on field bunds or dykes to protect them from erosion. In low lying areas, generally in close vicinity to water, vetiver grasses are used to control drainage channels, field dykes and roadsides. Vetiver is used as roofing material for poor huts and occasionally as fodder. But in hilly areas use of hedgerows as barriers is rare. Unfortunately soil erosion is severe in this part of Bangladesh. Shoaib et all (1998) estimated that about 5500 ha of lands are used for shifting and/or root crop cultivation each year without any conservation measures. Total loss of soil is about 2.5 mt yr^-1. However valleys of hills are broad based tabletop terraced and field bunds (dykes) are working as raisers. The batters of these raisers are usually 1:1 of height 0.5 to 1.0m and covered by grasses (C. ductylon).

Source of Information: Source: SRDI 2001. Soil Resources in Bangladesh: Assessment and Utilization. Proceedings of the annual workshop on soil resources. 14-15 February, 2001. SRDI, Dhaka.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: Not estimated

Total Budget (Tk.) : Not estimated

Achievement/Findings:

A project of ICIMOD initiated hedgerow cultivation in hills through SALT program of CHTDB in Bangladesh. They started the job by using leguminous shrub crops. The results are shown in tabular form. Biomass yield from different species as found at SALT station at Alutotila pruned 3 times at 20cm height is also given. In 1996 SCWMC started experiments on controlling erosion in shifting cultivation by using hedgerow on steep slope. It includes vetiver as one of the hedge species from 1997. Soil loss and run-off were estimated from 100m² plots by multislot divisors and hedge species at different parts of the slope. The species are Tephrosia candida, Indigofera, Napier and Vetiver. The Tephrosia candida hedge is three years old, therefore it shows less soil loss in relation to others. Two years average results are given in table and figure. The calculation was done for steep slope where the hedgerows are at 1m vertical intervals and expected total length of the row will be approximately 3000m. Management costs were also calculated on same assumption. Performances of these species were also observed in terms of growth rate, survival and propagation. Among them Tephrosia is the best at the initial stage but survival rate is least after three years, where vetiver performed best from the second year of its establishment. It needs least maintenance and easy to propagate although the initial growth rate is very low.

Knowledge Management: Report/Proceedings